EP4705368A1

EP4705368A1 - Phase separated optically clear adhesives

Info

Publication number: EP4705368A1
Application number: EP24724637.4A
Authority: EP
Inventors: Tianyu Wu; Encai Hao; Ying Xia; Yongshang Lu; Jason D. Clapper
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2023-05-02
Filing date: 2024-05-01
Publication date: 2026-03-11
Also published as: WO2024228124A1; CN121127512A

Abstract

Curable compositions include at least one (meth)acrylate-functional polyurethane polymer, at least one first (meth)acrylate monomer having a low homopolymer Tg of less than or equal to -10°C, at least one second ethylenically unsaturated monomer having polar content, and at least one initiator. The(meth)acrylate-fimctional polyurethane polymer is formed from aliphatic polyisocyanate, polyester polyol, and a hydroxyl-functional or isocyanate-functional (meth)acrylate. The curable composition, upon curing in the form of a layer forms a pressure sensitive adhesive layer or a heat activated adhesive layer that is phase separated and is optically clear having a haze value of less than 1%.

Description

PA101303W003

PHASE SEPARATED OPTICALLY CLEAR ADHESIVES

Summary

Disclosed herein are curable compositions and articles that include cured layers of the curable compositions. In some embodiments, the curable composition comprises at least one (meth)acrylate-functional polyurethane polymer, at least one first (meth)acrylate monomer having a low homopolymer Tg of less than or equal to -10°C of Formula 4:

CH₂=CR¹-(CO)-O-R³

Formula 4 where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O. R³ is linear or branched alkyl group with 4-24 carbon atoms, at least one second ethylenically unsaturated monomer having polar content, and at least one initiator. The(meth)acrylate- functional polyurethane polymer is the reaction product of a reaction mixture comprising at least one aliphatic polyisocyanate, at least one polyester polyol, and a hydroxyl- functional or isocyanate-functional (meth)acrylate. The second ethylenically unsaturated monomer having polar content is a vinyl functional polar monomer or a (meth)acrylate of Formula 5:

CH₂=CR¹-(CO)-O-R⁵

Formula 5 where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O, R⁵ is an -R⁴-(X)_P group or a polyether group, R⁴ is a linear or branched p+1 valent aliphatic group with at least 2 carbon atoms, X is a polar group comprising a hydroxyl group, a nitrogencontaining group, or an acid group, p is an integer of 1 or greater. The curable composition, upon curing in the form of a layer forms a pressure sensitive adhesive layer or a heat activated adhesive layer that is phase separated and is optically clear having a haze value of less than 1%.

Also disclosed are articles comprising a substrate with a cured layer of the curable composition described above.

-1-

SUBSTITUTE SHEET (RULE 26) Brief Description of the Drawings

The present application may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings.

Figure 1 is a graph showing the rheology data for Example 3 (Ex-3) and Comparative Example 1 (CEx-1) of this disclosure

Figure 2 is an Atomic Force Microscopy image of an adhesive layer of Example 2 (Ex-2) of this disclosure showing phase separation.

Figure 3 is an Atomic Force Microscopy image of an adhesive layer of Example 3 (Ex-3) of this disclosure showing phase separation.

Figure 4 is. an Atomic Force Microscopy image of a comparative adhesive layer of Comparative Example 1 CEx-1 of this disclosure showing no phase separation.

Detailed Description

A wide range of optical articles have multiple layers. The multiple layers often are adhered to each other with adhesive layers. These adhesive layers have a wide range of desired or required properties. Achieving some properties is very complex process. Adhesive layers are designed to adhere together two films or substrates, but additional properties are also generally required of the adhesive layers. Many of these properties are difficult to achieve since imparting a new property to the adhesive layer cannot be achieved by sacrificing adhesive properties.

Optically clear adhesives (optical grade adhesives that can be pressure sensitive adhesives, heat activated adhesives or structural adhesives are hereinafter referred to as “OCA”) are widely used in a wide variety of articles and have increasingly stringent property requirements. Optically clear adhesives are enabling components within electronic display devices, serving to reduce light refraction, improve clarity, bond functional elements of the display together, and provide insulating protection from environmental stressors such as impact events. Impact resistance is becoming increasing important in optical articles as devices become thinner and have more sensitive components.

-2-

SUBSTITUTE SHEET (RULE 26) One technique that may be suitable for increasing impact resistance is to have an adhesive layer with a phase separated morphology. For example, rubber toughened structural adhesives have both high strength and high toughness. However, such compositions are typically heterogeneous and optically opaque. Therefore, the need remains for OCAs that have a phase separated morphology without sacrificing the optical properties.

In this disclosure are described a series of curable adhesive compositions that, upon curing, exhibit unique rheological characteristics with in-situ phase separated domains. The phase separation can be detected in a variety of ways including the use of rheological measurements such as DMA (Dynamic Mechanical Analysis) and surface analysis techniques such as AFM (Atomic Force Microscopy). The resulting adhesive remains optically clear, suggesting phase separated morphologies on a sub-micrometer scale. In particular, phase separation typically results in high haze, but the current adhesive layers have a low haze. The cured adhesive layers also exhibit excellent adhesion to glass, making them attractive for OCA applications.

While not wishing to be bound by theory, it is believed that the selection of the reactive materials used in the curable compositions provide the balance of properties, namely phase separation without sacrificing the optical and adhesive properties. In particular, the different rates of reactivity of acrylates and methacrylates is one of the factors that controls the morphology of the cured adhesive layer, permitting phase separation without creating phase separated domain sizes that are so large as to interfere with the optical properties of the adhesive layer. Additionally, the compatibility of the polyurethane and (meth)acrylate monomers plays a role, both in affecting the polymerization and in the final polymer.

Disclosed herein are curable compositions comprising at least one (meth)acrylate- fimctional polyurethane polymer, at least one first (meth)acrylate monomer having a low homopolymer Tg of less than or equal to -10°C, at least one second ethylenically unsaturated monomer having polar content, and at least one initiator. The curable composition may also contain additional co-polymerizable monomers. Each of these materials is described in detail below.

The curable composition, upon curing in the form of a layer, forms a pressure sensitive adhesive layer or heat activated adhesive layer that is phase separated, having a

-3-

SUBSTITUTE SHEET (RULE 26) DMA (Dynamic Mechanical Analysis) spectrum when scanned at 3°C/minute at a frequency of 1 Hertz, contains a very broad Tan Delta peak with a FWHM (Full Width at Half Maximum) of at least 30°C. In some embodiments, the FWHM is 50°C, 70°C, or even 100°C. In some embodiments, two separate Tan Delta peaks (a low Tg Tan Delta peak and a high Tg Tan Delta peak) are observed in the DMA spectrum.

Also disclosed are articles prepared with the curable compositions. The articles comprise a substrate and a layer of the cured curable composition.

The term “adhesive” as used herein refers to polymeric compositions useful to adhere together two adherends. Examples of adhesives are pressure sensitive adhesives, heat activated adhesives, and structural adhesives.

Pressure sensitive adhesive compositions are well known to those of ordinary skill in the art to possess properties including the following: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be cleanly removable from the adherend. Materials that have been found to function well as pressure sensitive adhesives are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power. Obtaining the proper balance of properties is not a simple process.

Heat activated adhesives are non-tacky at room temperature but become tacky and capable of bonding to a substrate at elevated temperatures. These adhesives usually have a Tg or melting point (Tm) above room temperature. When the temperature is elevated above the Tg or Tm, the storage modulus usually decreases, and the adhesive becomes tacky.

Structural adhesives refer to adhesives that that can bond other high strength materials (e.g., wood, composites, or metal) so that the adhesive bond strength is in excess of 6.0 MPa (1000 psi).

The term “(meth)acrylate” refers to monomeric acrylic or methacrylic esters of alcohols. Acrylate and methacrylate monomers or oligomers are referred to collectively herein as "(meth)acrylates”. Materials referred to as “(meth)acrylate functional” are materials that contain one or more (meth)acrylate groups.

The terms "room temperature" and "ambient temperature" are used interchangeably to mean temperatures in the range of 20°C to 25°C.

-4-

SUBSTITUTE SHEET (RULE 26) The terms “Tg” and “glass transition temperature” are used interchangeably. If measured, Tg values are determined by Differential Scanning Calorimetry (DSC) at a scan rate of 10°C/minute, unless otherwise indicated. Typically, Tg values for copolymers are not measured but are calculated using the well-known Fox Equation, using the monomer Tg values provided by the monomer supplier, as is understood by one of skill in the art.

The term “adjacent” as used herein when referring to two layers means that the two layers are in proximity with one another with no intervening open space between them. They may be in direct contact with one another (e.g. laminated together) or there may be intervening layers.

The terms “polymer” and “macromolecule” are used herein consistent with their common usage in chemistry. Polymers and macromolecules are composed of many repeated subunits. As used herein, the term “macromolecule” is used to describe a group attached to a monomer that has multiple repeating units. The term “polymer” is used to describe the resultant material formed from a polymerization reaction.

The term “aliphatic” refers to hydrocarbon groups that are free from aromatic groups.

The term “alkyl” refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. The alkyl can be linear, branched, cyclic, or combinations thereof and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.

The term “alkylene” refers to a divalent group that is a radical of an alkane. The alkylene can be straight-chained, branched, cyclic, or combinations thereof. The alkylene often has 1 to 20 carbon atoms. In some embodiments, the alkylene contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The radical centers of the alkylene can be on the same carbon atom (i.e., an alkylidene) or on different carbon atoms.

The term “aromatic” refers to aryl groups, the term “aryl” refers to a monovalent group that is aromatic and carbocyclic. The aryl can have one to five rings that are connected to or fused to the aromatic ring. The other ring structures can be aromatic, nonaromatic, or combinations thereof. Examples of aryl groups include, but are not limited

-5-

SUBSTITUTE SHEET (RULE 26) to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perylenyl, and fluorenyl.

The term “heteroalkylene” refers to a divalent group that includes at least two alkylene groups connected by a thio, oxy, or -NR- where R is alkyl. The heteroalkylene can be linear, branched, cyclic, substituted with alkyl groups, or combinations thereof. Some heteroalkylenes are polyoxyalkylenes where the heteroatom is oxygen such as for example, -CH2CH2(OCH2CH2)nOCH₂CH2-.

The terms “free radically polymerizable” and “ethylenically unsaturated” are used interchangeably and refer to a reactive group which contains a carbon-carbon double bond which is able to be polymerized via a free radical polymerization mechanism.

Unless otherwise indicated, the terms “optically transparent”, and “visible light transmissive” are used interchangeably, and refer to an article, film or adhesive that has a high light transmittance over at least a portion of the visible light spectrum (about 400 to about 700 nm). Typically, optically transparent articles have a visible light transmittance of at least 90% and a haze of less than 10%.

Unless otherwise indicated, "optically clear" refers to an adhesive or article that has a high light transmittance over at least a portion of the visible light spectrum (about 400 to about 700 nm), and that exhibits low haze, typically less than about 5%, or even less than about 2%. In some embodiments, optically clear articles exhibit a haze of less than 1% at a thickness of 50 micrometers or even 0.5% at a thickness of 50 micrometers. Typically, optically clear articles have a visible light transmittance of at least 95%, often higher such as 97%, 98% or even 99% or higher.

Disclosed herein are curable compositions comprising at least one (meth)acrylate- functional polyurethane polymer, at least one first (meth)acrylate monomer having a low homopolymer Tg of less than or equal to -10°C, at least one second ethylenically unsaturated monomer having polar content, and at least one initiator. The at least one (meth)acrylate-functional polyurethane polymer is the reaction product of at least one aliphatic polyisocyanate, at least one polyester polyol, and a hydroxyl-functional or isocyanate -functional (meth)acrylate .

In some embodiments, the curable composition comprises at least one (meth)acrylate-functional polyurethane polymer, at least one acrylate-functional first

-6-

SUBSTITUTE SHEET (RULE 26) monomer, and at least one non-acrylate-functional second monomer, where the nonacrylate-functional monomer comprises a methacrylate or an ethylenically unsaturated monomer.

The curable composition comprises at least one (meth)acrylate -functional polyurethane polymer. The at least one (meth)acrylate-functional polyurethane polymer is the reaction product of a reaction mixture comprising at least one aliphatic polyisocyanate, at least one polyester polyol, and a hydroxyl-functional or isocyanate-functional (meth)acrylate. Each of these components of the reaction mixture are described in greater detail below.

Typically, the polyurethane polymer is formed by forming a pre-polymer by reacting the at least one aliphatic polyisocyanate and the at least one polyester polyol. The pre-polymer is either isocyanate-functional or hydroxyl-functional depending upon the ratio of the at least one aliphatic polyisocyanate, to the at least one polyester polyol. The prepolymer is then end-capped by reacting with either a hydroxyl-functional or isocyanate-functional acrylate, methacrylate of combination thereof.

In some embodiments, the at least one aliphatic polyisocyanate is of Formula 1:

(OCN-L)n-A

Formula 1 where A is an n-valent aliphatic group, L is single bond or an alkylene linking group; n is an integer of 2 or greater.

In some embodiments, the at least one aliphatic polyisocyanate of Formula 1 comprises a di-isocyanate where A is an alkylene group with at least 6 carbon atoms, L is single bond, and n is an integer of 2.

Examples of particularly suitable polyisocyanates include the liquid cycloaliphatic di-isocyanates commercially available from Covestro of Leverkusen, Germany under the trade name “DESMODUR” such as DESMODUR W, DESMODUR H, DESMODUR I and VESTANT TMDI (a mixture of 2,2,4- and 2,4,4-trimethyl-hexamethylene diisocyanate), VESTANT IPDI from Evonik Corporation of Theodore, AL hexamethylenediisocyanate and Isophoronediisocyanate from Vencorex Chemicals, Freeport, TX.

-7-

SUBSTITUTE SHEET (RULE 26) The reaction mixture also comprises at least one polyester polyol. In some embodiments, the at least one polyester polyol is of Formula 2:

(HO)m-B

Formula 2 where B is an m-valent aliphatic group with at least one polyester linkage, and m is an integer of 2 or greater.

In some embodiments, the at least one polyester polyol of Formula 2 comprises a polyester diol of at least 500 molecular weight where B is a di -valent aliphatic group with at least one polyester linkage, m is an integer of 2.

In some embodiments, the polyester diol is prepared from the condensation reaction of a di-acid and a diol, where at least one of the di-acid and the diol comprise an alkylene group with at least 12 carbon atoms. In some embodiments, it may be desirable the alkylene group with at least 12 carbon atoms be a branched alkylene group.

Examples of particularly suitable polyester polyols include the dimerized fatty acid-based polyester polyols from Croda Ince, Edison, NJ under the trade name “PRIPLAST” such as PRIPLAST 3196, PRIPLAST 3190, PRIPLAST 3238, PRIPLAST 3187, PRIPLAST 3188, PRIPLAST 3186, PRIPLAST 1838, PRIPLAST 3172, PRIPLAST 3197, PRIPLAST 3286 and PRIPLAST 3293. and combinations thereof.

In some embodiments, it may be desirable to include a polyol of Formula 7: D-((E-OH)-Y)_a

Formula 7 where D is an n-valent aromatic, aliphatic, or alkylene oxide group, E is an alkylene oxide linking group, Y is a (meth)acrylate group, and a is an integer of 2 or greater. An advantage of including this type of monomer is that the (meth)acrylate group is already attached to the polyol and thus does not need to react with a compound of Formula 3 as described below.

Examples of suitable compounds of Formula 7 are the DENACOL ACRYLATE materials commercially available from Nagase ChemteX Corporation as DA-911, DA- 920, DA-931, DA-212, DA-214, DA-250, DA-721, and DM-201

Typically, if used, the polyol of Formula 7 is a minor component of the reaction mixture and additional polyols as described above, are also present in the reaction mixture.

-8-

SUBSTITUTE SHEET (RULE 26) In some embodiments, it is desirable that the functionality of the pre-polymer formed by the reaction of a polyisocyanate and polyol have a functionality of less than 2. It is well understood that the reaction of a diol and a diisocyanate forms a linear difunctional prepolymer. To form a prepolymer with a functionality of less than 2, at least some of the reactants have a functionality of less than 2. In these embodiments, some of the reactants included in the reaction mixture are monofunctional. In some of the embodiments, the reaction mixture comprises at least some reactants that are monofunctional such that the average functionality of the prepolymer is greater than 1 and less than 2. This prepolymer upon reaction with the (meth)acrylate-functional compound described below forms the (meth)acrylate -functional polyurethane. Therefore, in these embodiments, the (meth)acrylate-functional polyurethane polymer has a functionality of greater than 1 and less than 2.

Examples of suitable monofunctional reactants are described by Formula 8:

Z-L-K

Formula 8 where K is an aliphatic group, L is single bond or an alkylene linking group, and Z is a hydroxyl group or an isocyanate group.

The reaction mixture also comprises at least one acrylate, methacrylate, or a combination thereof of Formula 3:

CH₂=CR¹-(CO)-O-R²-Z

Formula 3 where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O, R² is linear or branched alkylene group with at least 2 carbon atoms, and Z is an isocyanate-reactive group or hydroxyl-reactive group. Examples of isocyanate-reactive groups include hydroxyl groups, acid groups, and amino groups. Examples of hydroxyl-reactive groups include isocyanates, carboxylic acid groups, and anhydrides. Typically, the Z groups are isocyanates or hydroxyl groups.

As described above, the choice of whether the Z group is a hydroxyl group or an isocyanate group depends upon the relative ratio of the polyisocyanate and polyol components described above. If the polyisocyanate is present in excess so that the growing polymer is isocyanate-functional, the acrylate or methacrylate is hydroxyl- functional (i.e. reactive with isocyanate groups). If the polyester polyol is present in

-9-

SUBSTITUTE SHEET (RULE 26) excess so that the growing polymer is polyol-functional, the acrylate or methacrylate is isocyanate-functional (i.e. reactive with hydroxyl groups).

The choice of whether the component is an acrylate, methacrylate or a combination thereof depends upon the desired properties of the polyurethane polymer. Because acrylates and methacrylates react at different rates, the functionality of the polyurethane polymer provides a handle for controlling the ultimate properties of the formed adhesive layer.

In some embodiments, the at least one acrylate, methacrylate, or a combination thereof of Formula 3 is a hydroxyl-functional (meth)acrylate where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O, R² is linear or branched alkylene group with at least 2 carbon atoms, and Z is a hydroxyl group.

Examples of particularly suitable hydroxyl-functional (meth)acrylates include HEA (hydroxyl ethyl acrylate), HEMA (hydroxyl ethyl methacrylate), HPA (hydroxyl propyl acrylate), HPMA (hydroxyl propyl methacrylate), HBA (hydroxyl butyl acrylate), and HBMA (hydroxyl butyl methacrylate).

The kinetics of the polymerization between the polyisocyanate and polyol species is typically accelerated with the help of a suitable catalyst. In exemplary embodiments, the (meth)acry late -functional polyurethane polymer is prepared using any of a wide variety of known urethane catalysts, including dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, triethylene diamine, zirconium catalysts, and bismuth catalysts.

In some embodiments, the at least one (meth)acry late -functional polyurethane polymer has a number average molecular weight of at least 4000 grams/mole.

Besides the above-described at least one (meth)acrylate -functional polyurethane polymer, the curable composition comprises additional reactive components. Again, as was described above, while not wishing to be bound by theory, it is believed that the selection of the reactive materials used in the curable compositions provide the balance of properties, namely phase separation without sacrificing the optical and adhesive properties. In particular, the different rates of reactivity of acrylates and methacrylates is one of the factors that controls the morphology of the cured adhesive layer, permitting phase separation without creating phase separated domain sizes that are so large as to interfere with the optical properties of the adhesive layer. The at least one (meth)acrylate- functional polyurethane polymer can have either acrylate of methacrylate groups or a

-10-

SUBSTITUTE SHEET (RULE 26) combination thereof, and the additional reactive components likewise can be acrylates, methacrylates, vinyl-functional or a combination thereof.

The amount of (meth)acrylate-functional polyurethane polymer present in the curable composition can vary widely. Typically, the (meth)acrylate-functional polyurethane polymer is present in an amount of at least 10% by weight based upon the total weight of the curable components of the curable composition. In some embodiments, the (meth)acrylate-functional polyurethane polymer is present in an amount of 20%, 40%, 50%, 60% by weight or greater.

The curable composition also comprises at least one first (meth)acrylate monomer having a low homopolymer Tg of less than or equal to -10°C. In some embodiments, the first (meth)acrylate monomer is of Formula 4:

CH₂=CR¹-(CO)-O-R³

Formula 4 where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O, R³ is linear or branched alkyl group with 4-24 carbon atoms.

Examples of suitable first (meth)acrylate monomers include butyl acrylate, hexyl acrylate, 2-ethylhyexyl acrylate, iso-octyl acrylate. Examples of suitable monomers include, but are not limited to: 2-ethylhexyl (meth)acrylate, pentyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, n-nonyl (meth)acrylate, isoamyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isobomyl (meth)acrylate, cyclohexyl (meth)acrylate, isostearylacrylate 2-methylbutyl (meth)acrylate, and combinations thereof. Other suitable monomers include the branched long chain acrylates described in U.S. Patent No. 8,137,807, and the secondary alkyl acrylates described in U.S. Patent 9,399,724.

The curable composition also comprises at least one second ethylenically unsaturated monomer having polar content. The second ethylenically unsaturated monomer can be a vinyl-functional polar monomer or a (meth)acrylate of Formula 5:

CH₂=CR¹-(CO)-O-R⁵

Formula 5 where R¹ is an H or a methyl group. (CO) is a carbonyl group C=O, R⁵ is an -R⁴-(X)_P group or an alkylene oxide group; R⁴ is a single bond or a linear or branched p+1 valent

-11-

SUBSTITUTE SHEET (RULE 26) aliphatic group with at least 2 carbon atoms, X is a polar group comprising a hydroxyl group, a nitrogen-containing group, or an acid group, p is an integer of 1 or greater.

Examples of suitable vinyl-functional polar monomers include vinyl amide monomers such as acrylamide, N,N-dimethyl acrylamide, acryloylmorpholine, N-vinyl caprolactam, N-vinyl pyrrolidone. Other vinyl-functional polar monomers include 4-vinyl methyl oxazolidinone, vinyl oxazoline, and vinyl imidazole.

Examples of suitable polar copolymerizable acid-functional monomers include, but are not limited to, acrylic acid (AA), methacrylic acid, itaconic acid, fumaric acid. Examples of hydroxyl containing monomers include 2-hydroxyethyl (meth)acrylate, and 2 -hydroxy-propyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate. Alkylene oxidecontaining monomers (where R⁵ is an alkylene oxide group) include 2-ethoxyethoxyethyl (meth)acrylate, 2-methoxyethoxyethyl(meth)acrylate, as well as monomers where R⁵ contains repeating units of the type -CH2-CHR^a-0- where R^a is a hydrogen atom or a methyl group.

In addition to the monomers described above, the curable composition includes a free radical initiator to commence polymerization of the monomers. The free radical initiator can be a photoinitator or a thermal initiator. The amount of the free radical initiator is often in a range of 0.05 to 5 weight percent based on a total weight of monomers used.

In many embodiments, a photoinitiator is used. Some exemplary photoinitiators are benzoin ethers (e.g., benzoin methyl ether or benzoin isopropyl ether) or substituted benzoin ethers (e.g., anisoin methyl ether). Other exemplary photoinitiators are substituted acetophenones such as 2,2-diethoxyacetophenone or 2,2-dimethoxy-2- phenylacetophenone (commercially available under the trade designation Omnirad 651 from IGM resins (Charlotte, NC, NJ, USA), 1 -hydroxy cyclohexyl phenyl ketone (commercially available under the trade designation OMNIRAD 184 from iGM Resins) and 2 -hydroxy-2 -methyl- 1 -phenyl propan- 1 -one (available as OMNIRAD 1173 from iGM Resins). Or under the trade designation ESACURE KB-1 from Sartomer (Exton, PA, USA)). Still other exemplary photoinitiators are substituted alpha-ketols such as 2- methyl-2-hydroxypropiophenone, aromatic sulfonyl chlorides such as 2- naphthalenesulfonyl chloride, and photoactive oximes such as 1 -phenyl- 1,2-propanedione- 2-(O-ethoxycarbonyl)oxime. Particularly suitable photoinitiators include, for example,

-12-

SUBSTITUTE SHEET (RULE 26) Bis(2,4,6-Trimethylbenzoyl)phenylphosphine oxide (commercially available under the trade designation Omnirad 819 from IGM resins), 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide (commercially available under the trade designation Omnirad TPO from IGM resins), and ethyl(2,4,6-trimethylbenzoyl)-phenyl phosphinate (commercially available under the trade designation Omnirad TPO-L from IGM resins)

The curable composition may also contain other co-polymerizable monomers. In some embodiments, the curing composition further comprises at least one third (meth)acrylate monomer having a high Tg of at least 0°C of Formula 6:

CH₂=CR¹-(CO)-O-R⁶

Formula 6 where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O, R⁶ is linear, branched, or cyclic alkyl group.

Examples of suitable third monomers include isobomyl acrylate, isobomyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, TMCHA (3,3,5-trimethylcyclohexyl acrylate), tetrahydrofurfuryl acrylate, and tetrahydrofurfuryl methacrylate.

As with the other reactive components of the curable composition, the third monomer, if used, can help to control the final morphology of the cured adhesive layer. Therefore, the selection of an acrylate-functional third monomer or methacrylate- functional third monomer relates to the nature of the other reactive components in the curable composition.

Additionally, the curable composition may contain a photocrosslinkable monomer. Examples of these monomers are ones that contain an aromatic ketone group. When exposed to ultraviolet radiation, the aromatic ketone group can abstract a hydrogen atom from another polymeric chain or from another portion of the polymeric chain. This abstraction results in the formation of radicals that can subsequently combine to form crosslinks between polymeric chains or within the same polymeric chain. In many embodiments, the aromatic ketone group is an aromatic ketone group such as, for example, a derivative of benzophenone, acetophenone, or anthraquinone. Examples of photocrosslinkable monomers include ABP (Acryloyl benzophenone).

Other materials can be added to the monomer mixture for special purposes, including, for example: molecular weight control agents, coupling agent, oils, plasticizers,

-13-

SUBSTITUTE SHEET (RULE 26) antioxidants, UV stabilizers, UV absorbers, pigments, curing agents, polymer additives, nanoparticles, and other additives. In cases where the assembly layer needs to be optically clear, other materials can be added to the monomer mixture, provided that they do not significantly reduce the optical clarity of the assembly layer after polymerization and coating.

The curable compositions can be disposed on a surface and cured to form an optically clear pressure sensitive adhesive layer or heat active adhesive layer. The cured pressure sensitive adhesive layer or heat active adhesive layer has a wide range of desirable properties. As mentioned above the pressure sensitive adhesive layer or heat active adhesive layer is phase separated. Phase separation can be detected in a variety of methods. One method for describing phase separation is through the use of DMA (Dynamic Mechanical Analysis). The DMA spectrum when scanned at 3°C/minute at a frequency of 1 Hertz, contains a very broad Tan Delta peak with a FWHM (Full Width at Half Maximum) of at least 30°C. In some embodiments, the FWHM is 50°C, 70°C, or even 100°C. In some embodiments, two separate Tan Delta peaks (low Tg tan delta peak and high Tg tan delta peak) are observed in DMA spectrum.

Another method for detecting the phase separation of the OCA is by AFM (Atomic Force Microscopy). Phase separation can be detected in the AFM scan through the observation of phase separated microdomains. Atomic force microscopy (AFM) is a powerful technique that enables the imaging of almost any type of surface, including polymers, ceramics, composites, glass and biological samples. AFM is used to measure and localize many different forces, including adhesion strength, magnetic forces and mechanical properties. In some embodiments, the phase separated microdomains have at least one dimension of at least 40 nanometers and less than 200 nanometers. In some embodiments, the phase separated microdomains have at least one dimension of less than 150 nanometers.

As has been mentioned above, the desirable phase separation is achieved without sacrificing the desirable optical properties of the pressure sensitive adhesive or heat activated adhesive layer. In particular, the phase separated pressure sensitive or heat activated adhesives have low haze values. The haze of the pressure sensitive or heat activated adhesive is less than 1%. Haze can be a function of thickness, so typically hazes is measured on samples of a thickness of 50 micrometers or greater. Haze can be

-14-

SUBSTITUTE SHEET (RULE 26) measured, for example with a spectrophotometer. Typically, the pressure sensitive or heat activated adhesive has a transmission of at least 90% and has a clarity of at least 95%.

Additionally, to be useful in optical applications, the pressure sensitive or heat activated adhesive layers also have high adhesion. Typically, this adhesion is tested by 180° Peel Adhesion to a substrate such as glass. The current adhesives have a 180° Peel Adhesion at room temperature to glass of greater than 5 Newtons/centimeter. As mentioned above, pressure sensitive adhesives are typically laminated at room temperature, whereas heat activated adhesives are heated to a temperature above the Tg or Tm of the adhesive prior to lamination.

Also disclosed herein are adhesive articles. In some embodiments, the articles comprise a substrate with a first major surface and a second major surface; and a pressure sensitive adhesive layer or heat activated adhesive layer disposed on at least a portion of the second major surface of the substrate. The pressure sensitive adhesive or heat activated adhesive layer is the reaction product of a curable composition comprising at least one (meth)acrylate-functional polyurethane polymer, at least one first (meth)acrylate monomer having a homopolymer Tg of less than or equal to -10°C, at least one second ethylenically unsaturated polar monomer, and at least one initiator. The at least one (meth)acrylate-functional polyurethane polymer is the reaction product of at least one aliphatic polyisocyanate, at least one polyester polyol, and a hydroxyl-functional or isocyanate-functional (meth)acrylate. The at least one first (meth)acrylate monomer having a homopolymer Tg of less than or equal to -10°C is of Formula 4:

CH₂=CR¹-(CO)-O-R³

Formula 4 where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O, R³ is linear or branched alkyl group with 4-24 carbon atoms. The at least one polar monomer is a vinyl functional amide or a (meth)acrylate of Formula 5:

CH₂=CR¹-(CO)-O-R⁵

Formula 5 where R¹ is an H or a methyl group, (CO) is a carbonyl group C=O, R⁵ is an -R⁴-(X)_P group or a polyether group, R⁴ is a linear or branched p+1 valent aliphatic group with at least 2 carbon atoms, X is a polar group comprising a hydroxyl group, a nitrogencontaining group, or an acid group, and p is an integer of 1 or greater. The curable

-15-

SUBSTITUTE SHEET (RULE 26) composition also comprises at least one initiator. The curable compositions and the components used to generate the curable composition are described above.

In some embodiments, the curable composition may comprise additional co- polymerizable monomers such as at least one third (meth)acrylate monomer having a high Tg of at least 0°C of Formula 6:

CH₂=CR¹-(CO)-O-R⁶

The pressure sensitive adhesive layer or heat activated adhesive layer is phase separated, having a DMA (Dynamic Mechanical Analysis) spectrum when scanned at 3°C/minute at a frequency of 1 Hertz, contains a very broad Tan Delta peak with a FWHM (Full Width at Half Maximum) of at least 30°C. In some embodiments, the FWHM is 50°C, 70°C, or even 100°C. In some embodiments, two separate Tan Delta peaks (a low Tg Tan Delta peak and a high Tg Tan Delta peak) are observed in the DMA spectrum. Additionally, despite the phase separation of the adhesive layer it is optically transparent having a haze value of less than 1%. These properties and the other desirable properties of the adhesive layers prepared from the curable compositions are described above.

The articles comprise an optically clear substrate with a first major surface and a second major surface. A wide range of optically clear substrates are suitable. Examples of suitable optically clear substrates include polymeric films, and plates.

Polymeric films include, for example polyvinyl chloride, polyurethane (e.g., thermoplastic polyurethanes), polyester (e.g., polyethylene terephthalate (“PET”), polyethylene naphthalate (“PEN”), and polylactic acid copolymer), polycarbonate, polyacrylate, polymethyl(meth)acrylate (“PMMA”), polyvinylbutyral, polyimide, polyamide, fluoropolymer, cellulose acetate, triacetyl cellulose (TAC), ethyl cellulose, polyolefins (e.g. biaxially oriented polypropylene (BOPP)), and polycyclic olefin polymers (“COP”).

Examples of optically clear plates include plates made from glass, polycarbonate, or polymethylmethacrylate.

The articles also comprise a phase separated pressure sensitive adhesive layer or heat activated adhesive layer disposed on at least a portion of the second major surface of

-16-

SUBSTITUTE SHEET (RULE 26) the substrate. The pressure sensitive adhesive or heat activated adhesive layer is prepared by coating the curable composition on the substrate surface and curing the curable composition. Typically, curing is carried out by exposure to UV light to activate the initiator. The pressure sensitive adhesive layer or heat activated adhesive layer can have a wide range of thicknesses. In some embodiments, the pressure sensitive adhesive layer has a thickness of from 10 micrometers to 1 millimeter. Examples

These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims. All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, unless noted otherwise. Solvents and other reagents used were obtained from Sigma-Aldrich Chemical Company; Milwaukee, Wisconsin unless otherwise noted. The following abbreviations are used: nm = nanometers; mm = millimeters; cm = centimeters; in = inch; Hz = Hertz; min = minutes; h = hours; mJ = milliJoules; FWHM = Full Width at Half Maximum.

Table of Abbreviations

-17-

SUBSTITUTE SHEET (RULE 26)

Test Methods

Haze and transmission

Transmission measurements were made using an ULTRASCANPRO Spectrophotometer (HunterLab, Reston, VA) in transmission mode. For measured samples, a 0.1 mm thick coated adhesive layer between release-coated carrier liners (Liner- l/Liner-2, as described in the Examples below was cut to approximately 5 cm width by 10 cm length. One of the carrier liners was removed and the sample was

-18-

SUBSTITUTE SHEET (RULE 26) laminated to a clear piece of 1 mm thick LCD glass (Swift Glass, Elmira Heights, New York). The second carrier liner was removed, and the sample was placed in the ULTRASCANPRO Spectrophotometer to measure transmission and color through the glass/OCA assembly. Transmission at specific wavelengths were recorded and listed in Table below.

180° Peel on glass:

This peel adhesion test is similar to the test method described in ASTM D 3330- 90, substituting a glass substrate for the stainless steel substrate described in the test.

The cured adhesive samples were first laminated onto a 2 mil (51 micrometer) primed PET backing (3 SAB from Mitsubishi). They were then slit into 1 cm strips and rolled onto glass substrates with a Cheminstruments HR- 100 roller. The test specimens were allowed to condition in a CTH room for 18 h prior to peel adhesion analysis with a 6 cm/min peel rate at a 180° peel angle using a IMass SP-2000 peel tester.

Rheology Test Method.

The specimens for the rheological analysis were prepared by folding the 4 mil (102 micrometer) adhesive specimens into 800 micrometer thickness. The folded OCA sample was then cut into a disc with an 8 mm die and loaded into a Discovery HR-3 rheometer from TA Instruments with an 8 mm parallel plate geometry. The rheology test was conducted with a heating, or cooling, rate of 3°C/min and a 1 Hz Oscillation frequency.

Atomic Force Microscope:

AFM samples were prepared by cutting adhesive into small squares and fastened on a glass slide with double-side tape. Easy liner was peeled off and tapping AFM test was performed on the easy liner surface. The AFM equipment is a Bruker (Veeco, digital instruments). The AFM studies were performed using tapping mode, which is a dynamic AFM technique that images the sample topography by scanning the surface with an oscillating cantilever. Tapping mode uses the amplitude of cantilever oscillation to detect changes in the tip-sample interaction forces and thereby the sample topography. In tapping mode, the cantilever vibrates with amplitudes and the tip makes intermittent contact with the sample surface during the measurement. The amplitude is used as topography

-19-

SUBSTITUTE SHEET (RULE 26) feedback, while the phase lag between drive and detected signal contains information about material-specific mechanical properties. The AFM image shown in the application is the phase image. The phase image is of a different nature - it is a map of how the phase of the AFM cantilever oscillation is affected by its interaction with the surface. The physical meaning of this signal is complex. Generally, the contrast generated in phase imaging is a map of material property differences such as composition, adhesion and viscoelasticity. Darker regions in a phase image typically correspond to areas with lower stiffness while brighter regions correspond to areas with higher stiffness. In addition, the phase signal is sensitive to step edges and can generate a topography-induced phase contrast.

Gel Permeation Chromatography (GPC)

The molecular weight distribution of the polyurethane polymers was characterized using gel permeation chromatography (GPC). The GPC instrumentation, which was obtained from Waters Corporation (Milford, MA, USA), included a high pressure liquid chromatography pump (Model 1515HPLC), an auto-sampler (Model 717), a UV detector (Model 2487), and a refractive index detector (Model 2410). The chromatograph was equipped with two 5 micrometer PL gel MIXED-D columns available from Varian Inc. (Palo Alto, CA,USA).

Samples of polymeric solutions were prepared by dissolving dried polymer samples in tetrahydrofuran at a concentration of 1.0 percent (weight/volume) and filtering through a 0.2 micrometer polytetrafluoroethylene fdter that is available from VWR International (West Chester, PA, USA). The resulting samples were injected into the GPC and eluted at a rate of 1 milliliter per minute through the columns maintained at 35°C. The system was calibrated with polystyrene standards using a linear least squares analysis to establish a standard calibration curve. The number average molecular weight (Mn) was reported.

Examples

Synthesis Examples: Preparation of Polyurethane-(meth)acrylates

Preparative example of polyurethane (meth)acrylate (PU-1)

To a resin reaction vessel equipped with a mechanical stirrer, a condenser, and an air inlet, 200 gram (g) of Polyol-1, 18.50 g of DI-1, 0.21 g of BC, 0.08 g of BHT and 50 g

-20-

SUBSTITUTE SHEET (RULE 26) of MEK were added. The solution was heated up to 75°C while stirring. The temperature was maintained at 75±2° C until the NCO content reached the theoretical NCO value, which was determined by utilizing a standard dibutylamine back titration method. Upon obtaining the theoretical NCO value, the polyurethane was then end capped by adding 2.12 g of HEMA. During the reaction, an additional 70 g of MEK was added to dilute the viscosity of the mixture. After the reaction was completed, 220 g of 2-EHA was added, followed by the evaporation of MEK through a Rotavapor to obtain a polyurethane (meth)acrylate (number average molecular weight (Mn) = 5500 ) in 2EHA with a weight ratio of 1 : 1.

Preparative example of polyurethane (meth)acrylate (PU-2)

To a resin reaction vessel equipped with a mechanical stirrer, a condenser, and an air inlet, 205.6 gram (g) of Polyol-1, 15.77 g of DI-2, 0.22 g of BC, 0.08 g of BHT and 50 g of MEK were added. The solution was heated up to 75°C while stirring. The temperature was maintained at 75±2° C until the NCO content reached the theoretical NCO value, which was determined by utilizing a standard dibutylamine back titration method. Upon obtaining the theoretical NCO value, the polyurethane was then end capped by adding 2.88 g of HEMA. During the reaction, an additional 50 g of MEK was added to dilute the viscosity of the system. After the reaction was completed, 224 g of 2EHA was added, followed by the evaporation of MEK through a Rotavapor to obtain a polyurethane (meth)acrylate (Mn = 6300) in 2EHA with a weight ratio of 1 : 1.

Preparative example of polyurethane (meth)acrylate (PU-3)

To a resin reaction vessel equipped with a mechanical stirrer, a condenser, and an air inlet, 100.0 gram (g) of Polyol-2, 13.33 g of DI-2, 0.06 g of BC, 0.02 g of BHT and 50 g of MEK were added. The solution was heated up to 75°C while stirring. The temperature was maintained at 75±2° C until the NCO content reached the theoretical NCO value, which was determined by utilizing a standard dibutylamine back titration method. Upon obtaining the theoretical NCO value, the polyurethane was then end capped by adding 2.60 g of HEMA. During the reaction, an additional 20 g of MEK was added to dilute the viscosity of the system. After the reaction was completed, 115 g of

-21-

SUBSTITUTE SHEET (RULE 26) 2EHA was added, followed by the evaporation of MEK through a Rotavapor to obtain a polyurethane (meth)acrylate (Mn = 4900) in 2EHA with a weight ratio of 1 : 1.

Preparative example of polyurethane (meth)acrylate (PU-4)

To a resin reaction vessel equipped with a mechanical stirrer, a condenser, and an air inlet, 100.0 gram (g) of Polyol-3, 12.86 g of DI-2, 0.06 g of BC, 0.02 g of BHT and 50 g of MEK were added. The solution was heated up to 75°C while stirring. The temperature was maintained at 75±2° C until the NCO content reached the theoretical NCO value, which was determined by utilizing a standard dibutylamine back titration method. Upon obtaining the theoretical NCO value, the polyurethane was then end capped by adding 2.65 g of HEMA. During the reaction, an additional 20 g of MEK was added to dilute the viscosity of the system. After the reaction was completed, 115 g of 2EHA was added, followed by the evaporation of MEK through a Rotavapor to obtain a polyurethane (meth)acrylate (Mn = 7000) in 2EHA with a weight ratio of 1 : 1.

Examples Ex-1 - Ex-13 and Comparative Examples CE-1 - CE-6:

Preparation of curable formulations:

All curable formulations were prepared by adding the polyurethane polymers (as a 1: 1 mixture with 2-EHA), monomers, adhesion promoters and photo-initiators in %wt ratio as shown in Table 1. Typically, all materials were mixed together in a 8 oz amber jars and roller mixed for at least 8 h until the formulations were fully homogeneous.

Table 1.

Preparation of Adhesive Coatings

SUBSTITUTE SHEET (RULE 26) The adhesive formulations were first coated between two release liners (Liner- 1 and Liner-2 from SKC Haas) using a knife coater to control the coating caliper. The adhesive samples were fully cured under UV-LED light with a total dose of 2000 mJ/cm².

The samples were tested according to the test methods described above, and their data were summarized in Table 2.

Table 2: Performance of Adhesive Samples

Determination of Phase Separation in OCA samples:

Rheology Data:

Phase separation is demonstrated by rheology data as shown in Figure 1 which shows the data for Example 3 (Ex-3) and Comparative Example 1 (CEx-1). The graph shows that Example 3 has a tan delta spectrum with 2 peaks and is very broad.

AFM images:

Figures 2, 3, and 4 are AFM images for Examples Ex-2 and Ex-3 and Comparative Example CEx-1. Figures 2 and 3 clearly show phase separation. Figure 4 clearly shows a lack of phase separation. An AFM of Comparative Example CEx-2 (not shown) also fails to show phase separation, but shows a kind of phase morphology indicative of an interpenetration network of polymers. This phase morphology is uniform throughout the surface.

SUBSTITUTE SHEET (RULE 26)

Claims

What is claimed is:

1. A curable composition comprising: at least one (meth)acrylate-functional polyurethane polymer that is the reaction product of a reaction mixture comprising: at least one aliphatic polyisocyanate; at least one polyester polyol; and a hydroxyl-reactive or isocyanate-reactive (meth)acrylate; at least one first (meth)acrylate monomer having a low homopolymer Tg of less than or equal to -10°C of Formula 4:

CH₂=CR¹-(CO)-O-R³

Formula 4 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R³ is linear or branched alkyl group with 4-24 carbon atoms; at least one second ethylenically unsaturated monomer having polar content that is a vinyl functional polar monomers or a (meth)acrylate of Formula 5 :

CH₂=CR¹-(CO)-O-R⁵

Formula 5 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R⁵ is an -R⁴-(X)_P group or a polyether group;

R⁴ is a linear or branched p+1 valent aliphatic group with at least 2 carbon atoms;

X is a polar group comprising a hydroxyl group, a nitrogen-containing group, or an acid group; p is an integer of 1 or greater; and at least one initiator; wherein the curable composition, upon curing in the form of a layer forms a pressure sensitive adhesive layer or a heat activated adhesive layer that is phase separated and is optically clear having a haze value of less than 1 %.

-24-

SUBSTITUTE SHEET (RULE 26)

. The curable composition of claim 1, wherein the phase separation is determined by the pressure sensitive adhesive layer or heat activated adhesive layer having a DMA (Dynamic Mechanical Analysis) spectrum when scanned at 3°C/minute at a frequency of 1 Hertz, containing a Tan Delta spectrum having a FWHM (Full Width at Half Maximum) of at least 30°C.

3. The curable composition of claim 1, wherein the at least one (meth)acrylate-functional polyurethane polymer is the reaction product of a reaction mixture comprising: at least one aliphatic polyisocyanate of Formula 1:

(OCN-L)n-A

Formula 1 wherein A is an n-valent aliphatic group,

L is single bond or an alkylene linking group; n is an integer of 2 or greater; at least one polyester polyol of Formula 2:

(HO)m-B

Formula 2 wherein B is an m-valent aliphatic group with at least one polyester linkage, m is an integer of 2 or greater; and at least one isocyanate-reactive or hydroxyl-reactive acrylate, methacrylate, or a combination thereof of Formula 3:

CH₂=CR¹-(CO)-O-R²-Z

Formula 3 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R² is linear or branched alkylene group with at least 2 carbon atoms;

Z is a hydroxyl group or an isocyanate group.

4. The curable composition of claim 1, wherein the at least one (meth)acrylate-functional polyurethane polymer is the reaction product of a reaction mixture comprising:

-25-

SUBSTITUTE SHEET (RULE 26) at least one aliphatic di -isocyanate of Formula 1:

(OCN-L)n-A

Formula 1 wherein A is an alkylene group with at least 6 carbon atoms,

L is single bond; n is an integer of 2; at least one polyester diol with a molecular weight of at least 500 grams/mole of Formula 2:

(HO)m-B

Formula 2 wherein B is a di-valent aliphatic group with at least one polyester linkage, m is an integer of 2; and at least one acrylate, methacrylate, or a combination thereof of Formula 3 : CH₂=CR¹-(CO)-O-R²-Z

Formula 3 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R² is linear or branched alkylene group with at least 2 carbon atoms;

Z is a hydroxyl group.

5. The curable composition of claim 1, wherein the at least one (meth)acrylate-functional polyurethane polymer has a number average molecular weight of at least 4000 grams/mole.

6. The curable composition of claim 1, wherein the hydroxyl -reactive or isocyanatereactive (meth)acrylate comprises formula 7 :

D-((E-OH)-Y)_a

Formula 7 wherein D is an n-valent aromatic, alkylene oxide, or aliphatic group;

E is an alkylene oxide linking group;

Y is a (meth)acrylate group; and a is an integer of 2 or greater.

-26-

SUBSTITUTE SHEET (RULE 26)

7. The curable composition of claim 1, wherein the reaction mixture further comprises at least one monofunctional compound of formula 8:

Z-L-K

Formula 8 wherein K is an aliphatic group,

L is single bond or an alkylene linking group;

Z is a hydroxyl group or an isocyanate group.

8. The curable composition of claim 1, further comprising: at least one third (meth)acrylate monomer having a high Tg of at least 0°C of Formula

6:

CH₂=CR¹-(CO)-O-R⁶

Formula 6 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R⁶ is linear, branched, or cyclic alkyl group.

9. The curable composition of claim 1, further comprising at least one photocrosslinking monomer.

10. The curable composition of claim 1, wherein upon curing to form a pressure sensitive adhesive layer or heat activated adhesive layer, the adhesive layer has phase separated microdomains, detectable by AFM (Atomic Force Microscopy) wherein the phase separated microdomains have at least one dimension that is less than 150 nanometers.

11. The curable composition of claim 1, wherein upon curing to form a pressure sensitive adhesive layer or heat activated adhesive layer, the adhesive layer has a 180° Peel Adhesion to glass of greater than 5 Newtons/centimeter.

-27-

SUBSTITUTE SHEET (RULE 26)

12. The curable composition of claim 1, wherein the curable composition is substantially acid free.

13. The curable composition of claim 1, wherein the at least one (meth)acrylate-functional polyurethane polymer is present in an amount of at least 10 % by weight based upon the total weight of the reactive components of the curable composition.

14. An article comprising: a substrate with a first major surface and a second major surface; and a pressure sensitive adhesive layer or heat activated adhesive layer disposed on at least a portion of the second major surface of the substrate, the pressure sensitive or heat activated adhesive layer being the reaction product of a curable composition comprising: at least one (meth)acrylate-fimctional polyurethane polymer that is the reaction product of a reaction mixture comprising: at least one aliphatic polyisocyanate; at least one polyester polyol; and a hydroxyl-reactive or isocyanate-reactive (meth)acrylate; at least one first (meth)acrylate monomer having a low homopolymer Tg of less than or equal to -10°C of Formula 4:

CH₂=CR¹-(CO)-O-R³

Formula 4 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R³ is linear or branched alkyl group with 4-24 carbon atoms; at least one second ethylenically unsaturated monomer having polar content that is a vinyl-functional polar monomer or a (meth)acrylate of Formula 5: CH₂=CR¹-(CO)-O-R⁵

Formula 5 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R⁵ is an -R⁴-(X)_P group or a polyether group;

-28-

SUBSTITUTE SHEET (RULE 26) R⁴ is a linear or branched p+1 valent aliphatic group with at least 2 carbon atoms;

X is a polar group comprising a hydroxyl group, a nitrogen-containing group, or an acid group; p is an integer of 1 or greater; and at least one initiator; wherein the pressure sensitive adhesive layer or heat activated adhesive layer that is phase separated and is optically transparent having a haze value of less than 1%.

15. The article of claim 14, wherein the phase separation is determined by the pressure sensitive adhesive layer or heat activated adhesive layer having a DMA (Dynamic Mechanical Analysis) spectrum when scanned at 3°C/minute at a frequency of 1 Hertz, containing a Tan Delta spectrum having a FWHM (Full Width at Half Maximum) of at least 30°C.

16. The article of claim 14, wherein the substrate comprises an optically clear substrate comprising a polymeric film or a plate.

17. The article of claim 14, wherein the at least one (meth)acrylate-functional polyurethane polymer is the reaction product of a reaction mixture comprising: at least one aliphatic polyisocyanate of Formula 1:

(OCN-L)n-A

Formula 1 wherein A is an n-valent aliphatic group, L is single bond or an alkylene linking group; n is an integer of 2 or greater; at least one polyester polyol of Formula 2:

(HO)_m-B

Formula 2 wherein B is an m-valent aliphatic group with at least one polyester linkage,

-29-

SUBSTITUTE SHEET (RULE 26) m is an integer of 2 or greater; and at least one isocyanate-reactive or hydroxyl-reactive acrylate, methacrylate, or a combination thereof of Formula 3:

CH₂=CR¹-(CO)-O-R²-Z

Formula 3 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R² is linear or branched alkylene group with at least 2 carbon atoms;

Z is a hydroxyl group or an isocyanate group.

18. The article of claim 14, wherein the at least one (meth)acrylate-functional polyurethane polymer is the reaction product of a reaction mixture comprising: at least one aliphatic di -isocyanate of Formula 1:

(OCN-L)n-A

Formula 1 wherein A is an alkylene group with at least 6 carbon atoms,

L is single bond; n is an integer of 2; at least one polyester diol with a number average molecular weight of at least 500 grams/mole of Formula 2:

(HO)m-B

Formula 2 wherein B is a di-valent aliphatic group with at least one polyester linkage, m is an integer of 2; and at least one acrylate, methacrylate, or a combination thereof of Formula 3

CH₂=CR¹-(CO)-O-R²-Z

Formula 3 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R² is linear or branched alkylene group with at least 2 carbon atoms;

Z is a hydroxyl group.

-30-

SUBSTITUTE SHEET (RULE 26)

19. The article of claim 14, wherein the at least one (meth)acrylate-functional polyurethane polymer has a number average molecular weight of at least 4000 grams/mole

20. The article of claim 14, further comprising: at least one third (meth)acrylate monomer having a high Tg of at least 0°C of Formula

6:

CH₂=CR¹-(CO)-O-R⁶

Formula 6 wherein R¹ is an H or a methyl group;

(CO) is a carbonyl group C=O;

R⁶ is linear, branched, or cyclic alkyl group.

21. The article of claim 14, wherein the pressure sensitive adhesive layer or heat activated adhesive layer has phase separated microdomains detectable by AFM (Atomic Force Microscopy), wherein the phase separated microdomains have at least one dimension that is less than 200 nanometers.

22. The article of claim 14, wherein the pressure sensitive adhesive layer has a thickness of from 10 micrometers to 1 millimeter.

-31-

SUBSTITUTE SHEET (RULE 26)